Research On Greening Design Strategy Of Sponge Street Valley In Guanzhong Area Based On Microclimate

Street Valley not only undertakes the important task of urban transportation,but the quality of its local physical environment also closely affects the thermal comfort of pedestrians in Street Valley.The Guanzhong area centered on Xi'an is hot in summer and the thermal comfort of street valleys with different aspect ratios is quite different.Domestic studies have shown that greening has a certain effect on improving the street valley microclimate with a uniform aspect ratio,but in different aspect ratios.In the street valley,the influence of greening on the street valley's microclimate and thermal comfort remains to be studied.Therefore,from the perspective of greening variable design,there is an urgent need and broader practical significance for the research on improving the microclimate environment of street valleys with different aspect ratios in Guanzhong area.Through literature and field research and research,greening structure,tree planting density,and tree crown size are selected as the street valley greening elements that affect the street valley microclimate environment,and the aspect ratio is 0.5,the aspect ratio is 1,and the aspect ratio is 2.Street valleys are representative of street valleys with large differences in thermal comfort.In order to understand and analyze the microclimate characteristics of the Sponge Street Valley in detail and comprehensively,and to verify the rationality and scientificity of the microclimate numerical simulation model,this article first selects representative sponge Street Valleys to conduct surveys on the microclimate in winter and summer.After verifying the rationality of the numerical simulation model,the ENVI-met software was used to carry out a numerical simulation study of the street valley microclimate based on the measured data.The test results show that the surface temperature and the wet black bulb temperature of the permeable asphalt road significantly decrease after the rain,but the reduction time is limited;the presence or absence of greenery has a greater impact on the microclimate of the street valley in summer than in winter,and the impact of trees on the microclimate of street valley pedestrian space is much greater The effect of the grass belt on the air temperature and the average radiant temperature depends on the canopy size and planting density of the shadow on the coverage of the street canyon.A quantitative simulation analysis of the greening factors affecting the microclimate of the street valley shows that the height-to-width ratio of the street valley and the street valley greening together affect the thermal comfort of the street valley.The greater the street valley aspect ratio,the less the solar radiation heat gains,the better the street valley thermal comfort.Well,greening has a limited effect on improving thermal comfort in street valleys.In general,the positive effect of greening on thermal comfort in street valleys with H/W=0.5>H/W=1 street valley>H/W=2 street valleys.Changes in the greening structure,canopy size,and planting density may have completely opposite effects on the thermal comfort of street valleys with large differences in solar radiation.For example,if the height-to-width ratio is 2 street valleys,the arbor reduces the wind speed to the thermal comfort.The negative impact is significantly greater than the positive impact of the shade on the average radiant temperature and air temperature on the thermal comfort of the street valley.A single green grass belt or shrub belt is more suitable for a street valley with H/W=2,and H/W=2 When setting arbor in the street valley,the small canopy arbor is better than the large canopy arbor.When the outer edges of the two arbor canopies are 1-3 meters apart,the thermal comfort of street valley is the best;for the aspect ratio of 0.5 and 1 street valley In general,arbor can significantly improve the comfort of street valley heat.